Inclusion Criteria:

1. Diagnosis of myelofibrosis requiring therapy, including those previously treated and
relapsed or refractory, or if newly diagnosed, with intermediate or high risk
according to Lille scoring system (risk factors are: Hb < 10 g/dl, WBC < 4 or > 30 x
109/L; risk group: 0 factor(s) = low, 1 factor(s) = intermediate, 2 factor(s) = high)
or with symptomatic splenomegaly

2. Understanding and voluntary signing an IRB-approved informed consent form.

3. Age >/= 18 years at the time of signing the informed consent.

4. Disease-free of prior malignancies for >/= 2-years with exception of basal cell or
squamous cell carcinoma of the skin, or carcinoma "in situ" of the cervix or breast.

5. ECOG performance status 0 to 2.

6. Patients must have adequate organ function as demonstrated by the following: Total
bilirubin (unless higher due to MF); Absolute neutrophil count >/= 1 x 10^9/L; ALT upper limit of normal (unless higher due to MF).

7. Females of childbearing potential (FCBP)† must have a negative serum or urine
pregnancy test with a sensitivity of at least 50 mIU/mL within 10 - 14 days prior to
and again within 24 hours of starting lenalidomide and must either commit to
continued abstinence from heterosexual intercourse or begin TWO acceptable methods of
birth control, one highly effective method and one additional effective method AT THE
SAME TIME, at least 4 weeks before she starts taking lenalidomide. FCBP must also
agree to ongoing pregnancy testing.

8. Continuation of 7. Men must agree to use a condom during sexual contact with a female
of child bearing potential even if they have had a successful vasectomy. All patients
must be counseled at a minimum of every 28 days about pregnancy precautions and risks
of fetal exposure. See Appendix J: Risks of Fetal Exposure, Pregnancy Testing
Guidelines and Acceptable Birth Control Methods

9. footnote to no 7. † A female of childbearing potential is a sexually mature woman
who: 1) has not undergone a hysterectomy or bilateral oophorectomy; or 2) has not
been naturally postmenopausal for at least 24 consecutive months (i.e., has had
menses at any time in the preceding 24 consecutive months).

10. All study participants must be registered into the mandatory RevAssist® program, and
be willing and able to comply with the requirements of RevAssist®.

Exclusion Criteria:

1. Use of any other standard (e.g. hydroxyurea, anagrelide, growth factors) or
experimental drug or therapy within 28 days of starting lenalidomide and/or lack of
recovery from all toxicity from previous therapy to grade 1 or better.

2. Known prior clinically relevant hypersensitivity reaction to thalidomide, including
the development of erythema nodosum if characterized by a desquamating rash.

3. Prior therapy with lenalidomide.

4. Any serious medical condition, laboratory abnormality, or psychiatric illness that
would prevent the subject from signing the informed consent form.

5. Suspected Pregnancy. Pregnant or lactating females.

6. Any condition, including the presence of laboratory abnormalities, which places the
subject at unacceptable risk if he/she were to participate in the study or confounds
the ability to interpret data from the study.

7. Known positive for HIV or infectious hepatitis, type A, B or C.

8. Known prior clinically relevant hypersensitivity to prednisone.

9. Participants with a heart rate (HR) of less than or equal to 50, as a HR less than 50
indicates underlying cardiac abnormalities.

10. Participants with prior history of thromboembolic disease (i.e.-deep venous
thrombosis [DVT] or pulmonary embolism [PE]) within the last six months, as
Lenalidomide has demonstrated a significantly increased risk of DVT or PE.